Influence of lighting environment on social preferences in sticklebacks from two different photic habitats.I.mate preferences of wild-caught females

Ultraviolet(UV)A signals(320-400 nm)are important in mate choice in numerous species.The sensitivity for UV signals is not only assumed to be costly,but also expected to be a function of the prevailing ecological conditions.Generally,those signals are favored by selection that efficiently reach the receiver.A decisive factor for color signaling is the lighting environment,especially in aquatic habitats,as the visibility of signals,and thus costs and benefits,are instantaneously influenced by it.Although ecological aspects of color signal evolution are relatively well-studied,there is little data on specific effects of environmental UV-light conditions on signaling at these shorter wavelengths.We studied wild-caught gravid female 3-spined sticklebacks Gasterosteus aculeatus of 2 photic habitat types(tea-stained and clear-water lakes),possessing great variation in their UV transmission.In 2 treatments,tea-stained and clear-water,preferences for males viewed under UV-present(UV-1-)and UV-absent(UV-)conditions were tested.A preference for males under UV+conditions was found for females from both habitat types,thus stressing the significance of UV signals in stickleback's mate choice decisions.However,females from both habitat types showed the most pronounced preferences for males under UV-h conditions under clear-water test conditions.Moreover,reflectance measurements revealed that the carotenoid-based orange-red breeding coloration in wild-caught males of both habitat types differed significantly in color intensity(higher in clear-water males)and hue(more red shifted in clear-water males)while no significant differences in UV coloration were found.The differential reflection patterns in longer wavelengths suggest that sticklebacks of both habitat types have adapted to the respective water conditions.Adaptations of UV signals in a sexual context to ambient light conditions in both behavior and coloration seem less evident.

The roles of inter- and intra-sexual selection in behavioral isolation between native and invasive pupfishes

Male-male competition and female mate choice may both play important roles in driving and maintaining reproductive isolation between species. When previously allopatric species come into secondary contact with each other due to introductions, they provide an opportunity to evaluate the identity and strength of reproductive isolating mechanisms. If reproductive isolation is not maintained, hybridization may occur. We examined how reproductive isolating mechanisms medi- ate hybridization between endemic populations of the Red River pupfish Cyprinodon rubrofluviati- lis and the recently introduced sheepshead minnow C. variegatus. In lab-based dominance trials, males of both species won the same number of competitions. However, male C. rubrofluviatilis that won competitions were more aggressive than C, variegatus winners, and more aggression was needed to win against competitor C. variagatus than allopatric C. rubrofluviatilis. Duration of fights also differed based on the relatedness of the competitor. In dichotomous mate choice trials, there were no conspecific or heterospecific preferences expressed by females of either species. Our findings that male-male aggression differs between closely and distantly related groups, but female choice does not suggest that male-male competition may be the more likely mechanism to impede gene flow in this system.

Asymmetric reinforcement in Lucania killifish:assessing reproductive isolation when both sexes choose

Reinforcement can occur when maladaptive hybridization in sympatry favors the evolution of con-specific preferences and target traits that promote behav ioral isolation(BI).In many systems,enhanced BI is due to increased female preference for conspecifics.In others,BI is driven by male preference,and in other systems both sexes exert preferences.Some of these patterns can be atributed to classic sex-specific costs and benefits of preference.Alternatively,sex differences in conspecific preference can emerge due to asymmetric postzygotic isolation(e.g.,hybrid offspring from female A × male B have lower fitness than hybrid offspring from female B × male A),which can lead to asymmetric BI(e.g.,female A and male B are less likely to mate than female B and male A).Understanding reinforcement requires understanding how conspecific preferences evolve in sympatry.Yet,estimating conspecific preferences can be difficult when both sexes are choosy.In this study,we use Lucania killifish to test the hypothesis that patterns of reinforcement are driven by asymmetric postzygotic isolation between species.If true,we predicted that sympatric female Lucania goodei and sympatric male L.parva should have lower levels of BI compared with their sympatric counterparts,as they produce hybrid offspring with the highest fitness.To address the problem of measuring BI when both sexes are choosy,we inferred the contribution to BI of each partner using assays where one sex in the mating pair comes from an allopatric population with potentially low preference,whereas the other comes from a sympatric population with high prefer-ence.For one hybrid cross direction,we found that both female L.parva and male L.goodei have high contributions to BI in sympatry.In the other hybrid cross direction,we found that only female L.goodei contribute to BI.Sympatric male L.parva readily engaged in hybrid spawnings with allo-patric L.goodei females.These results indicate that both asymmetric postzygotic isolation and the traditional sex-specific costs to preference likely affect the nature of selection on conspecific prefer-ences and target traits.

Female mating status affects male mating tactic expression in the wolf spider Rabidosa punctulata

Males and females have conflicting interests on the frequency and outcomes of mating interactions.Males maximize their fitness by mating with as many females as possible,whereas choosy females often reduce receptivity following copulation.Alternative male mating tactics can be adaptive in their expression to a variety of mating contexts,including interactions with a relatively unreceptive mated female.Male Rabidosa punctulata wolf spiders can adopt distinctive mating tactics when interacting with a female,a complex courtship display,and/or a more coercive direct mount tactic that often involves grappling with females for copulation.In this study,we set up female mating treatments with initial trials and then paired mated and unmated females with males to observe both female remating frequencies and the male mating tactics used during the interactions.Males adopted different mating tactics depending on the mating status of the female they were paired with.Males were more likely to adopt a direct mount tactic with already-mated females and courtship with unmated females.Already-mated females were considerably less receptive to males during experimental trials,although they did remate 34%of the time,the majority of which were with males using a direct mount tactic.Whereas males adjusting to these contextual cues were able to gain more copulations,the observation of multiple mating in female R.punctulata introduces the potential for sperm competition.We discuss this sexual conflict in terms of the fitness consequences of these mating outcomes for both males and females.